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Questions tagged [offset]

A variable with a fixed coefficient of 1. Offsets are commonly used in Poisson regression to allow the modeling of rates instead of counts.

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62 views

How do I fit models with predetermined covariates?

I'm trying to fit a multiple linear regression model. It has 10 variables, 2 of which are specified (e.g. $\beta_4 = 0.5$, $\beta_7 = 0.77$). How do I go about fitting this in R? I need to find the ...
25 views

Poisson regression with custom offset and link

I have the following model $$Y \sim \operatorname{Poisson}\left(\frac{1}{1+\exp(\beta X)} E\right)$$ In other words, I have count data for Poisson process with exposure E and rate given by the ...
32 views

Is an offset term necessary for a count model of a behavior where subjects determine trial length?

We are modeling data from a behavioral study in which subject pairs' conversations are coded for specific types of utterances (say "Type A"). Subjects decide when their trial is over and we count Type ...
21 views

Log-linear model for contingency table with no fixed count

I have table of counts of born children with four two-level factor variables (mother smoker/nonsmoker, child born dead/alive, ..). I would like to use log-linear model to understand interactions of ...
32 views

Overdispersed poisson-distribution and offset --> standard errors?

I am modeling count data using R and doing a fixed-effects/random-effects model and thus limited on functions and therefore cannot use a quasipoisson model or negative binomial distribution, but ...
80 views

What type of data is needed for offset in a Poisson regression model - R

I am trying to do a Poisson regression using the following data, where infant deaths are shown per year for both North and South England. ...
19 views

Can I use Poisson regression to model prevalence ratios if I only have information on events?

I often used Poisson regression models to estimate prevalence ratios. However, in these cases my data contained information on the whole population, including events (1) and non events (0). ...
23 views

Statistical specification for a Regression with continuous finite range count like data

I am interested in explaining what kind of personal characteristics and work environment variables are associated with sickness absenteeism. My dependent variable is the total number of days a given ...
24 views

Interpretation of average marginal effect for proportion outcome in Poisson model with offset

To see the association of malaria prevalence with village level risk factors, I ran a Poisson model in r with the prevalence of malaria(y) as a dependent variable, altitude(x1) and Forestation(x2) as ...
111 views

How does offset in XGBoost is handled in binary:logistic objective function

I am working on a mortality prediction (binary outcome) problem with “base mortality probability” as my offset in the XGboost problem. I have used gbtree booster and binary:logistic objective function....
32 views

How to fit a gls model with a known slope

i want to fit a gls model (from nlme package) with a specified slope, so i can get the computed intercept for the best fit. I tried to set the slope with an offset. Althogh it works fine with lm, it ...
32 views

POISSON REGRESSION AND OFFSET VARIABLE [duplicate]

I am using a Poisson regression model with a count data. More specifically, my dependent variable is the number of children dead. My feeling is that I could use a Poisson model with an offset ...
49 views

Should I include offset in null negative binomial model for comparing to full model?

I'm modeling how various landscape and ecological factors affect the I'd like to evaluate how well my negative binomial model performs over the null. I've specified an offset variable in my model to ...
54 views

Offset term in negative binomial regression

I am fitting a simple negative binomial regression model with (Yearly cancer death ~ Offset (Size of population) + Age + Household income). I used the offset term because I want to compare the yearly ...
264 views

Residual Deviance and degrees of freedom - Negative Binomial Distribution

I am trying to model count data using python's statsmodels module (Beer's sold at a football stadium as function of visitors, "tilskuer", and weather data). ...
73 views

Logistic regression with coefficients penalized to other numbers

When you penalize logistic regression using l1, l2 or both penalizations, the coefficients are penalized towards 0. I would like to do the same thing but penalizing the coefficients towards other ...
179 views

Negative Binomial Regression: Offset Variable and Dispersion Parameter

My case is that previously it's assumed that the counts of events follows a negative binomial distribution, and the annualized exacerbation rate is 1 with a dispersion parameter of 1.5, and all 500 ...
27 views

Offset in NB model produces contradictory results to original data

My (example) data frame is rather simple. I would like to know if there is a difference in numbers between the factors (n=2) within variable X. ...
117 views

Mixed Effect Model - Roadkill hotspot v. coldspot

This problem concerns road mortality. We have 4 highway sections of varied length that were flagged as problem areas for road mortality with large mammals (moose, deer, elk, and even cows). We used ...
251 views

binomial glm with null-hypothesis = 0.33

I have a dataset and need to test if the values are statistical different to 0.33 (=1/3). Flies have the choice between 3 types of berries. So, if they do not care about the type they would lay 1/3 of ...
88 views

Poisson distribution: how to calculate the expected number of zeros in the presence of an exposure term

I have a dataset each with a line for different products, a count of sales and a number of days on sale. I estimated a Poisson regression to predict sales with an offset term of number of days on sale,...
67 views

Can I model incidence per 1000 people per month using poisson regression without an offset or using weights?

I am trying to model incidence rates (number of malaria cases per 1000 people per month) over time. I only have the data in the form of rates per 1000 people per month, i.e. I do not know the total ...
142 views

How does Poisson regression (with an offset) relate to Logistic regression?

I have some data I am trying to analyze of how often someone has chosen a given option (which I'll call choice A) vs not choosing it (which I'll call choice B) during a 6 month period. Each subject ...
496 views

Offset option in Proc Logistic (SAS)

What difference does it make in estimation of model equation if a variable is specified in offset option in proc logistic? I know, if I specify a variable in offset option; the variable will be ...
57 views

Count data with “double offsets”?

I am looking into race and homicides in the USA, 1995-2016. I want to look into "trans-race" (victim and perpetrator different races) homicides by race and year. However I want to also include effects ...
88 views

Regression Relationship Between Fraction and Whole Number

I am trying to determine the best regression model to use to determine if there is a relationship between clicks (independent variable) (represented as a whole ...
481 views

Confidence interval for mean of Poisson distribution witih observations of different length

I am struggling with calculating a confidence interval for my data using a Poisson distribution. The context is manufacturing process quality control, and I think that a Poisson distribution is the ...
30 views

How to account for different baselines when analysing extremes in time series data

I want to see if Wikipedia articles for topics featured in popular documentaries get a boost in page views on the day the documentary is aired. I then want to see if time on screen is a predictor of ...
601 views

GLM with averaged-count data - Poisson? Negative Binomial? Offset?

I am trying to construct GLMs to explore the relationship between woodpecker abundance and 9 predictor variables (tree density, canopy cover, and so on). My data were collected as counts of ...
26 views

Include predictions as feature in regression. covariate or offset?

I have a regression setting in which I would like to explore the influence of a given variable on a certain patient condition, given a level of risk for the same outcome, predicted with a more complex ...
430 views

Gamma regression and offset term

I'm testing the effect of soil treatments on root and shoot length of seeds of a species. However the seeds had different sizes, which may affect root and shoot development. I have a measure of the ...
179 views

gamma mixed model with offset and/or weights

I have some continuous positive data $Y_{ij}$ representing accumulated quantities, where $i$ denotes subject and $j$ a state. Patients are transitioning across states sequentially, but not all ...
154 views

Applying offset correctly in an Interrupted Time Series Analysis using segmented regression in GLM in R [closed]

I would like to apply an offset to allow for the population within segmented regression using GLM on count data in R and need to ensure that the formula I am using is correct. Adding offset in 2 ...
1k views

why is XGBoost giving me seriously biased predictions with small nrounds?

I can not put my company data online, but I can provide a reproducible example here. We're modelling Insurance's frequency using Poisson distribution with exposure as offset. Here in this example, ...
1k views

Using glm() as substitute for simple chi square test

I am interested in changing the null hypotheses using glm() in R. For example: ...
43 views

Using an offset term with panel data and unexposed controls

I'm evaluating the effect of a policy change on a count outcome across a number of units over time. I have panel data for 300 units over 20 time periods, with roughly 20% of units exposed to the ...
2k views

How to interpret glm and ols with offset

I ran a few glm and linear models with an offset. Each row in the dataset is a healthcare user. The data contains medical payments and icu days of each user between 2000 to 2007. As the number of ...
132 views

Can a variable be used both as an offset and an independent variable?

I am developing a negative binomial regression model that investigates factors impacting the death rate of animals that are fed. The number of deaths was counted over the course of a feeding season, ...
334 views

offset in logistic regression to take into account a priori individual probability estimates

I am performing a logistic regression (LR) model on a set of data on which an initial probability estimate for event occurrence, sai $\hat{p_i}^{base}$ has been provided. I have supplementary ...
4k views

Can Weights and Offset lead to similar results in poisson regression?

In "A Practioner's guide to Generalized linear models" in paragraph 1.83 it is stated that: "In the particular case of a Poisson multiplicative GLM it can be shown that modelling claim counts with ...
47 views

How to insert temperature and precipitation data on a GEE or GLMM model

I am analysing a data of number of aphids with variation over time (32 avaliations performed every week), area (two areas), and plant position (fixed factor), with 3 replications. Because of that, I ...
1k views

Predict function on negative binomial produces strange fitted values when adding an offset

I have an over-dispersed count dataset and I want to add an offset to my negative binomial on the RHS to create a rate of events for y (see this great answer for ...
153 views

How can I account for different sampling effort in my GLMM Poisson regression using glmer() - easily reproduced example inc

I've been grappling with my dataset for what seems like a very long time now. Hope someone can point me in the right direction. I would like to know how to account for the differing sampling effort ...
36 views

Poisson regression on devices that fail during observation period?

I am observing N devices over a period of time $[0,T]$ and counting the number of certain events $y_j$, for each device, during that period of time. I also have some specifications $x_j$ for each ...
590 views

Offset in Poisson regression when using an identity link function?

It appears that in Poisson regression, using an identity link function means your betas will be rate differences, and using a log link function your (exponentiated) betas will be rate ratios. You can ...
4k views

Offset in Logistic regression: what are the typical use cases?

Offset is commonly used in Poisson regression to take into account different exposure (different time periods for instance): offset = log of exposure Question: ...
5k views

Difference between offset and exposure in Poisson Regression

Exposure and offset are two techniques often used in Poisson regressions by actuaries to predict claim frequency . From my understanding, offset and exposure are the same things, so I don't ...
357 views

Recalibration by regressing on intercept only with offset

Consider a risk prediction model developed on one population. When transporting this model to another population, the calibration can be off. There are several strategies for recalibration. One is to ...